Rockford Fosgate 351M manual Speaker Impedance, Installation, Using Passive Crossovers

INSTALLATION

10.Perform a final check of the completed system wiring to ensure that all connections are accurate. Check all power and ground connections for frayed wires and loose connections which could cause problems.

NOTE: Follow the diagrams for proper signal polarity.

!CAUTION: These amplifiers are not recommended for impedance loads below 2Ω.

USING PASSIVE CROSSOVERS

A passive crossover is a circuit that uses capacitors and/or coils and is placed on speaker leads between the amplifier and speaker. The crossover delegates a specific range of frequencies to the speaker for optimum driver performance. A crossover network can perform one of three functions: High-Pass (capacitors), Low- Pass (inductors or coils) and Bandpass (combination of capacitor and coil).

The most commonly used passive crossover networks are 6dB/octave systems. These are easy to construct and require one component per filter. Placing this filter in series with the circuit will reduce power to the speaker by 6dB/octave above or below the crossover point depending on whether it is a high-pass or low-pass filter. More complex systems such as 12dB/octave or 18dB/octave can cause impedance problems if not professionally designed.

Passive crossovers are directly dependent upon the speaker's impedance and component value for accuracy. When passive crossover components are used in multiple speaker systems, the crossover's effect on the overall impedance should be taken into consideration along with the speaker's impedance when determining amplifier loads.

CAUTION: These amplifiers

!are not recommended for impedance loads below 2Ω.

L

C

6dB/Octave Low-Pass

6dB/Octave High-Pass

Freq.

Speaker Impedance

Hertz

2 OHMS

4 OHMS

8 OHMS

L

C

L

C

L

C

80

4.1mH

1000µF

8.2mH

500µF

16mH

250µF

100

3.1mH

800µF

6.2mH

400µF

12mH

200µF

130

2.4mH

600µF

4.7mH

300µF

10mH

150µF

200

1.6mH

400µF

3.3mH

200µF

6.8mH

100µF

260

1.2mH

300µF

2.4mH

150µF

4.7mH

75µF

400

.8mH

200µF

1.6mH

100µF

3.3mH

50µF

600

.5mH

136µF

1.0mH

68µF

2.0mH

33µF

800

.41mH

100µF

.82mH

50µF

1.6mH

26µF

1000

.31mH

78µF

.62mH

39µF

1.2mH

20µF

1200

.25mH

66µF

.51mH

33µF

1.0mH

16µF

1800

.16mH

44µF

.33mH

22µF

.68mH

10µF

4000

.08mH

20µF

.16mH

10µF

.33mH

5µF

6000

51mH

14µF

.10mH

6.8µF

.20mH

3.3µF

9000

34mH

9.5µF

68mH

4.7µF

.15mH

2.2µF

12000

25mH

6.6µF

51mH

3.3µF

100mH

1.6µF

L = Low-Pass (Inductor)

C = High-Pass (Capacitor)

For more information, see your Authorized Rockford

Fosgate Dealer.

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